Early social traumas affect the developing individual both behaviorally and physiologically. As the incidence of HIV infection rises in adolescent populations, particularly those with numerous childhood traumas, an understanding of the impact of these events on disease resistance becomes increasingly important. Since studies of disease progression in HIV-infected humans are often confounded by factors such as drug use, it is imperative to develop a nonhuman primate model that can eliminate these influences. It has been shown that separating nonhuman primate infants from their mothers for a short period of time results in permanent alterations in the immune system. These take the form of enhanced natural cytotoxicity. What has not been determined is whether these changes are detrimental, i.e., result in increased risk for disease or rapid progression of the disease process following infection. In this study we are evaluating disease progression following inoculation with SIVsmE660 in 20 four-year-old pigtailed macaques. Half of the animals will have experienced a two-week maternal separation at six months of age and half will be matched controls from the same social group that have not been separated. The subjects have been part of an experimental protocol at the University of Colorado Health Sciences Center and their behavioral and immune development is well documented. Complete blood counts, differentials and flow cytometry before and after infection will be used to determine total numbers and proportions of lymphocytes as well as lymphocyte subsets (CD4+, CD8+, CD20+ and CD16+). Natural cytotoxicity to two tumor cell lines (K562 and Raji) will also be monitored. After infection, blood of all individuals will be examined for levels of antibody and virus by whole-virus enzyme-linked immunosorbent assay and polymerase chain reaction. Quantitative behavioral observations will also be collected on all subjects. Ten months after infection animals will be sacrificed and tissues examined for pathological changes. To date, one animal has arrived from Denver and has completed quarantine. This animal will be infected with SIVsmE660 in six weeks. Four more animals are scheduled to arrive early this spring.